In my books I didn't find much; Leslie Jackson states that engraved marks are post WW2, according to Heiremans they were used from the 1970s onwards.I found an interesting thread here on the board refering to a piece (probably) similar as 'Sasso Policromo' >> LinkUnfortunately all pics gone

Colours do look similar to many Gaspari pieces, but this may just be wishful thinking